Method and machine for manufacturing shaped parts from flat sheet metal

ABSTRACT

A method for the manufacture of shaped parts of elongate shape and having a variable cross-section from a strip of flat sheet metal. The method is characterised in that the strip of sheet metal is displaced along a generatrix of a shaping mandrel whose cross-section varies progressively along this generatrix in predetermined manner by decreasing dimensions, and in that the strip of sheet metal, as it is displaced, is progressively bent around the shaping mandrel on either side of said generatrix by appropriate pressure means which constrain it to follow the contour and dimensions at the point where their action is exerted, and in that the point of action of said pressure means is displaced along the spindle according to any appropriate law for producing a desired variation of section on the shaped part thus obtained. Such shaped parts may be the masts of pleasureboats, or support poles for the installation of external lighting.

United States Patent [191 Salata [451 Nov. 18, 1975 [30] ForeignApplication Priority Data Apr. 24, 1972 Switzerland 6050/72 [52] US. Cl.228/147; 29/33 D; 29/DIG. 41; 72/128; 72/129; 72/176; 228/17 [51] Int.Cl B23k 31/02; B2lk 29/00 [58] Field of Search 72/129, 177, 176, 128,72/52, 370, 159, 149; 29/DIG. 41, 477,

[56] References Cited UNITED STATES PATENTS 1,821,850 9/1931Riemenschneider 29/DIG. 41 2,581,673 1/1952 Kennedy 228/17 FOREIGNPATENTS OR APPLICATIONS 685,941 5/1964 Canada 72/176 Primary Examiner-C.W. Lanham Assistant Examine'r-Robert M. Rogers [57] ABSTRACT A methodfor the manufacture of shaped parts of elongate shape and having avariable cross-section from a strip of flat sheet metal. The method ischaracterised in that the strip of sheet metal is displaced along ageneratrix of a shaping mandrel whose crosssection varies progressivelyalong this generatrix in predetermined manner by decreasing dimensions,and in that the strip of sheet metal, as it is displaced, isprogressively 'bent around the shaping mandrel on either side of saidgeneratrix by appropriate pressure means which constrain it to followthe contour and dimensions at the point where their action is exerted,and in that the point of action of said pressure means is displacedalong the spindle according to any appropriate law for producing adesired variation of section on the shaped part thus obtained. Suchshaped parts may be the masts -of pleasure-boats, or support poles forthe installation of external lighting.

15 Claims, 6 Drawing Figures US. Patent Nov. 18, 1975 METHOD AND MACHINEFOR MANUFACTURING SHAPED PARTS FROM FLAT SHEET METAL This inventionrelates to the manufacture of shaped parts of elongated shape and whosecross-section varies progressively, such as, in particular, metal mastsfor pleasure-boats or support poles for carrying external lightingapparatus, panels, banners or like pieces of fabric. Masts of this typewhich, however, constitute only one of the possible numerousapplications of the present invention, are most frequently constitutedby tubular shaped parts of light alloy, which are between 6 and 10meters long and have a diameter which may vary between 50 to 150 mm;their cross-section is sometimes circular, sometimes oval and it maypossibly compriseone or more longitudinal grooves serving for anchoringaccessories, such for example as bolt-ropes, chainwales etc.

A first object of the present invention is to provide a method ofmanufacture by forming such shaped parts from a strip of flat sheetmetal.

One of the known methods for forming a metal shaped part from a flatmetal sheet consists in cold rolling the strip of sheet metal by passingit between pressure rollers which by successive bending operations, givethe shaped part any predetermined section; nevertheless, shapedpartsthus obtained may be only cylindrical and it is necessary to carry out asubsequent retreatment operation on the cylindrical tube thus obtainedif it is desired to obtain a shaped part having a section varyingprogressively, such, for example, as a slightly conical mast or pole.This re-treatment operation may, for example, consist in cutting alongitudinal notch in the shape of a very close Vin the tube andthereafter bringing the edges of the notch together and welding them. Aretreatment operation of this type complicates and makes the manufactureof such shaped parts difficult.

To produce shaped parts of progressively variable section from strips offlat sheet metal, it has been proposed to use a stationary shapingmandrel having a variable section determined by the shape of the shapedpart that it is desired to obtain and to press the strip of sheet metalagainst the periphery of this mandrel by means of an arrangement ofsuitable pressure rollers and associated actuating jacks displaceablewith respect to this mandrel. 1

Nevertheless, such a method does not lend itself to the production ofshaped parts having a closed or practically closed section since theshaping mandrel whose length is equal to that of the shaped part that itis desired to obtain, cannot be-cantilever supported on a stationaryframe owing to the magnitude of the bending stress to which it issubjected. In addition, the shaping mandrel is specific to a single typeof shaped part, both as regards length and section, and this constitutesa major industrial drawback, taking into account the cost of such toolsespecially where a limited manufacture of identical parts is envisaged.

The invention relates essentially to a method for the manufacture ofshaped parts of any length and having a closed or open section, varyingprogressively according to an entire desired range of variations, byshaping a strip of flat sheet metal on a single predetermined shapingmandrel.

To this end, the method of manufacture according to the invention ischaracterised in that the strip of sheet metal is displaced along ageneratrix of a shaping mandrel, whose cross-section variesprogressively along this generatrix in a predetermined manner bydecreasing dimensions, and in that the strip of sheet metal during isdisplacement, is progressively bent around the shaping mandrel'on bothsides of said generatrix by appropriate pressure means which impartthereto the shape and dimensions of the mandrel at the region wheretheir action is exerted, and in that the point of action of saidpressure means is displaced along the mandrel according to anyappropriate law for producinga desired variation of section on theshaped part thus obtained.

With such an arrangement, it will be seen that it is possible tomanufacture with a given shaping mandrel an entire range of shaped partsof different lengths and- /or cross-sections according to the law chosenfor the displacement of the point of action of the pressure means(pressure rollers) and the speed chosen for the travel of the strip ofsheet metal over the mandrel. In particular, it is possible to produceshaped parts'of great length with a relatively short shaping mandrel(order of magnitude 2m), which of course makes it possible to decreasethe manufacturing cost of the mandrel but above all to allow such amandrel to be cantilever mounted to the frame, which mounting isindispensable for facilitating the direct production of shaped partshaving a closed section (joined edges).

It should also be noted that by acting on the simultaneousdisplacements, with respect to the shaping mandrel, of the strip ofsheet metal and of the shaping head it is also possible to obtain shapedparts having at least partially either a constant cross-section or evena recess. Finally, the method of the invention allows high, speedproduction (of the order of l to 2 meters/minute for example) and lendsitself to continuous manufacture by imparting an appropriatereciprocating motion to the shaping head.

Another object of the invention is to provide a machine for carrying outthe abovedescribed method, which machine comprises a shaping mandrelhaving a cross-section decreasing progressively from its base andappropriately mounted in a fixed frame, and at least one shaping headwhich moves parallel to a generatrix of the spindle and supports atleast one pair of shaping rollers and associated actuating means forapplying a strip of flat sheet metal against the shaping mandrel on bothsides of said generatrix, and being characterised in that it alsocomprises first drive means for moving the strip of sheet metal at auniform speed along said generatrix and second drive means for thedisplacement of the shaping head with respect to the mandrel accordingto any appropriate predetermined law for producing the desired variationof section of the shaped part obtained.

An embodiment of the present invention will now be described, by way ofexample, with reference to the accompanying drawing, in which:-

FIG. 1 is a diagrammatic elevation of a machine according to theinvention and showing only the essential parts;

and,

FIGS. 2, 3, 4, 5 and 6 are detailed sectional views, to a larger scale,on the lines 11-", Ill-Ill, lV-IV, VV and Vl-Vl of FIG. 1, thesesections illustrating the successive stages of the method for formingthe shaped part from a strip of flat sheet metal. The machine comprisesa rigid frame comprising longitudinal girders an end support 2 fromwhich a shaping mandrel 3 is cantilever mounted. and another end support4 .on

other types of cross-section with respect to those of the shaped parttobe obtained; for this reason, the mandrel must be mounted on the frameof the machine so that it may be removed and interchanged. For carryingout the method according to the invention, it is onlyessential that theshaping spindle 3 has a cross-section decreasing progressively andhomothetically along its upper generatrix.

As illustrated in FIG. 1, the shaping mandrel 3 is secured to thesupport 2 with its axis slightly inclined above the horizontal by anangle suchthat its upper generatrix is substantially contained in thehorizontal plane extending the upper plane of the end support 2; thisarrangement ensures a virtually horizontal discharge of the shaped partas it is formed.

On the other hand, the machine includesa moveable shaping head 6comprising a rigid carriage 7 supporting shaping rollers and theiractuating mechanisms and movable along the longitudinal girders l of themachine frame, and a box 8 connected to the carriage 7 by a pivot 9which allows it to slide vertically, the box being guided in itsmovements by the inclined slides The inclination of the slides 5, whichmay be advantageously adjustable within certain limits, correspondssubstantially to that of the lower generatrix of the shaping spindle 3.It will thus be understood that when the carriage 7 moves along thehorizontal longitudinal girders l, the box 8 moves with it, while it is,in turn, displaced parallel to the lower generatrix of the shapingmandrel 3. The movements of the movable head 6 are controlled byconventional means, such, for example, as a screw control means 7adriven by an electric motor 71; and at a speed which is uniform orvariable according to the law of the desired variation of the dimensionsof the section on the shaped part to be obtained.

The moveable head 6 supports a succession of rollers 1 or groups ofmachining rollers staggered along the longitudinal axis of the shapingmandrel 3 and acting, one after the other, on the strip of sheet metal10 which moves forward in the direction of the arrow and at a uniformspeed along the upper generatrix of the mandrel. The respectivefunctions of these various rollers or groups of rollers will becomeclear on examining FIGS.3 to 6 of the drawing, assumed to correspond toone and the same position of the movable head 6 on the machine frame. a

A strip of flat sheet metal 10, which moves in contact substantiallyalong its longitudinal axis with the upper generatrixof the shapingmandrel 3, is firstly turned down through a certain angle on both sidesof this gene eratrix by a pre-shaping roller 1 1 having a concaveprofile and preferably made from a resilient material such as, forexample, rubber or a thermoplazstics, material having similarproperties.This roller 11,'which' is supported by a horizontal spindle integralwith the carriage 7 .rolls with sufficient pressure on the strip ofsheet metal 10, which it begins to turn down around the shaping mandrel3', as illustrated in FIG. 3 of the drawings. If necessary, otherpre-shapingrollers may be provided for assisting the action of theroller 11 or for completing it with a view to facilitating thesubsequent operation of the shapingrollers proper.

I 4 Shaping rollers 12 are at least two in number and may be supportedby the carriage 7 or by the box 8 of the. movable head 6 with their axessubstantially at'right angles to the axis of the shaping mandrel 3.These rollers:

12, also have a concave profile and are applied trans-,

versely and with substantial pressure on either side of the preformedmetal sheet 10 with a view to completing the bending around the shapingmandrel3 (FIG. 4).

In the embodiment illustratedin the drawing,,these shaping rollers 12are made from a material having ,resilient properties, for examplerubber and have I a groove profile corresponding substantially to theconfigurationand to the radius ofcurvature of the middle section of theshaping mandrel 3; owing to their elastic-.

employing mandrels of different dimensions on the same machine, theshafts of the shaping rollers 12 must.

be movable in a horizontaldirection transversely to the axis of themandrel. Thus, as far as possible, the necessary pressure must beprovided by actuating means developinga force independent of theirtravel. Preferably, to this end, the invention envisages employingoleopneumatic jacks of adjustable force depending on the thickness ofthe metal to be shaped.

According to theinvention, it is also possible to make use of thenatural adhesion of the rubber of the shaping rollers 12 to the strip ofsheet metal 10 so that they may also fulfil the function of means fordriving this strip of sheet metal along the shaping mandrel 3. To thisend, the rollers 12 may be set in rotation at a uniform speed and in thedesired direction by means of electric motors 12a provided withreduction gears or even by means or' rotary hydraulc motors. This makesany other means for controlling the forwards movement of the strip ofsheet metal 10 superfluous.

The shaping rollers above described seem the most appropriate for themanufacture of shaped parts of light alloys. Nevertheless, the numberand shape of the shaping rollers as well as their constituent materialmay vary depending on the sections of the shaped parts to be obtainedand on the nature of the metal used for their manufacture. Thus, forexample, in the case where the shaped parts are to be made of steel, itwould be suitable to substitute for the pair of rubber shaping rollersabove described, a group of rollers constituted by a hard material, forexample of polished steel, these rollers thus being distributed inpairs, two by two, on

opposed generatrices of the shaping mandrel.

' In this embodiment, when it is a question of producing a shaped parthaving a closed contour, in order to avoid material falling duringmanufacture, it would clearly be possible to give the strip of flatsheet metal 10 a width corresponding exactly to the length of thedeveloped circumference of the shaped part, this width thus clearlyhaving to vary along the strip of sheet, metal in order to take intoaccount the desired variation of dimensions of section on the shapedpart. Nevertheless, a

it is more simple to give the strip of roughtsheet metal an excess widthand to remove the superfluous. parts as V the shaped part, is produced,which superfluous parts could moreover be readily recovered,inlparticularin the case of light alloys. This operation may take placeby any appropriate means for example, sawing, shear.-

ing etc. Preference is given to a shearing operation which may inparticular be undertaken by means of steel rollers having an appropriatecuttingedge.

In order to obtain a clean cut such as to avoid a subsequentre-treatment operation, the superfluous lateral parts may advantageouslybe previously folded outwards by means of other steel rollers having astraight profile, the folding line thus imparted to the shaped partserving to guide the shearing rollers. The machine illustrated in theaccompanying drawingthus comprises, downstream of the shaping rollers12, a pair of folding rollers 13 and a pair of shearing rollers l4'bothsupported by the box 8 of the movable head 6, these steel rollers beingprovided with the same pressure means and being rotated in the samedirection and at the same tangential speed as the shaping rollers 12,but being displaced parallel to the lower generatrix of the shapingcylinder 3. FIG. 5 shows how therollers l3 finish off the shaping of thecontour of the shaped part by bending the superfluous parts 15 of thestrip of sheet metal substantially at right angles towards the outside.FIG. 6 shows how the shearing rollers 14, whose cutting edges roll inthe folding lines, detach the superfluous parts ls fromthe shaped part.

Still referring to the case ofmanufactureof a shaped part having aclosed contour, the movable'head 6 of the machine may also comprise,downstream of the shearing rollers 14, a spot or continuous weldingapparatus 18 which may be used to connectithe lips ofthejoint of theshaped part at the end of the shaping operations. The shaped part formedby'the abovedescribed machine progresses continuously along the shapingmandrel 3 and its shape as well as its sectional dimensions correspond,apart from the differences due to the thickness of the constituentmetal, to those of the section of the shaping mandrel 3 in the vicinityof which the'action of the folding rollers 13 is exerted. Naturally,under these conditions, if the movable head 6 does not move during theshaping operation, the shaped part obtained will be of uniform sectiondetermined as a function of the adjustment of the shaping head 6.Nevertheless, in the most general case when it is proposed to produce ashaped part having a variable'section, this result is obtained by anappropriate displacement of the shaping head 6 along thelongitudinal'girders 1 during the passage of the strip of sheet metal 10along the shaping mandrel 3. This displacement 'ofthe shaping headgenerally takes place at a speed less than that imparted to the strip ofsheet metal; by way of example, these speeds may be respectively0.3--m/mi'n and 1.8

m/min. Y t v Assuming that the passage of the strip of sheetmetal overthe shaping mandrel takes place at'-a constant speed, the law ofdisplacement of the shaping head itself depends on the law of desiredvariation of the sectional dimensions on the shaped part to be produced.While a uniform speed of movement of the head is translated in the caseof a frusto-conical shaping mandrel by a linear variation of thesectional dimensions along the axis of the shaped part, an appropriatecontrol of this speed as a function of times may facilitate, in thisparticular case, other laws of variation of the sectional dimensions,for example, parabolic, exponential etc., a possibility which isparticularly advantageous when it is proposed to obtain a solid memberof equal resistance to bending forces or compression (in the case ofships masts, for example). Such a control of the speed of displacementof the head may be obtained authe wall of the shaped part at the sametimeand in the same direction asthe dimensions of its section. Such aresult may be obtained easily with the method according to theinvention, since, for this purpose, it is sufficient to combine with theaforedescribed shaping machine, a rolling-mill between the rolls ofwhich the strip of rough sheet metal must pass before reaching theshaping mandrel. The spacing of the rolls of this rollingmill may bemodified duringthe operation, either man ually or preferably by means ofa controlmechanism itself controlled by the displacement of the shapingh'ead along the mandrel. Here also, the variation of thickness of thewall along the shaped part obtained may obey a linearlaw or anyotherappropriate law, the regulation of the mechanism controlling thespacing of the rolls being designed accordingly; it is also possible tomodify this spacing of the rolls discontinuously in order to obtain, ifneed be, sudden changes in the wall thickness of the shaped part. i

The cycle of operation for forming the shaped part may be precededand/or follow'edby any appropriate heat treatment. In particular, the'strip of rough sheet metal may be subjected to a continuous ordiscontinuous heat softening treatment by an apparatus 16, beforeitpasses to the shaping machine, the observation being made in this casethat by means of the method ac cording to the invention it is possibleto produce shaped parts of hard metals or alloys which 'are not suitedor ill-suitedto drawing. Likewise, the shaped part may be subjected atthe same time as the shaping operations to a continuous or discontinuoushead treatment by an apparatus 17 for restoring its characteristics,such as, for example, a hardening treatment able to impart theretocertain desired mechanical properties. 1

Although it has'not been expressly mentioned, the preceding descriptionimplicitly envisages the assumption of discontinuous production, thestrip of rough sheet metal being previously cut to the desired lengthand the width of thestrip being able to be cut in a flat condition, thusavoiding subsequent machining on the shaped part; the shaping head isthus operational only in one direction of displacement and at the end ofeach machining pass, it isrestored to its initial position ready for thenext pass. Nevertheless, the machine described is quite suitable forcontinuous production, in which the strip of sheet metal would unwindfrom a roll, the shaping head being in this case operational in bothdirections of displacement between its end positions. In this case, itwould be advisable to give the speed of displacement of the movable head6 and/or the speed of rotation of the shaping rollers 12 differentvalues in either of the two displacement directions of the head alongthe machine frame, and this would take into account the fact that in onedirection the speed of travel of the strip of sheet metal over theshaping mandrel 3 is equal to the sum of the tangential drive speed ofthe rollers 12 and the speed of movementof the head 6 with respect tothe shaping mandrel 3, whereas in the other direction, on the contrary,this same speed is equal to their difference. Thus, the machine deliverssuccessive lengths of shaped part having sections increasing anddecreasing alternately and it is an advantage to provide on the machineitself, an additional cutting apparatus designed for detaching thesesuccessive lengths of shaped part from each other, this apparatus movingin translation on the machine frame at the same speed as the strip ofsheet metal and thus as the shaped part throughout the duration of acutting operation and then returning automatically to itsinitial'position ready for the next operation.

Naturally, the preceding description is given only as an example and itin no way limits the possibilities for carrying out the method .offorming tubular shaped parts according to the claimed invention,.whichmay comprise numerous variations. Thus, in particular, the

shaping rollers could have no driving action on the. strip I of sheetmetal, the latter being drawn externally as on a drawing bench.

Finally, as a new industrial product, the invention ineludes tubularshaped partsobtained by applying the method described and/or by means ofa shaping machine such as that described above.

What is claimed is;

1. A method of manufacturing from a stripof flat sheet metal a shapedelongated part having a progressively varying cross section, comprising:displacing said strip along a generatrix of a fixed shaping mandrel thecross section of which decreases progressively along said generatrix ina predetermined manner, and progressively bending said strip as it isdisplaced around said mandrel on either side of said generatrix so as tofollow the shape and dimensions of said mandrel, by pressure means thepoint of action of which is variable along said mandrel to produce adesired variation in the cross sectionof the part to be shaped,

2. A method according to claim 1, which includes the step of cutting theedges of said strip after having been bent around said mandrel as theshaped part progresses along said mandrel by cutting means associatedwith said pressure means.

3. A method according to claim 2, which includes the 1 step of foldingsaid edges outwardly by folding means associated with said pressuremeans.

4. A method according to claim 3, wherein said cut ting means are guidedalongsaid mandrel by the fold:

line of the lateral edges produced by folding means.

5. A method according to claim 1, which includes subjecting said stripprior to said shaping step, to a soft- 7 treatment. a

7. A method according to claim 1, which includesthe step ofreciprocating said pressure means along said mandrel and cutting thethus obtained shaped partintermittentaly. 7

8. A machine for manufacturingf rom a strip of flat 1 sheet metal ashaped elongated part, comprisingza frame, a shaping mandrel mounted onsaid frame and having a cross section decreasingprogressively in onedirection at least one shaping head movable parallel to a generatrix ofsaid mandrel, at least one pair of shaping rollers and associatedactuating means supported 1 by said head for urging said strip againstsaid shaping mandrel on either side of, said generatrix, first drivemeans for displacing said strip at a uniform speed along saidgeneratrix, and second drive means for displacing said shaping head withrespect to said mandrel for producing the desired variationin crosssection of said.

and a stationary slide associated with saidmandrel for' guiding said boxin said transverse direction.

llLA machine according to claim 8, comprising at least one resilientpre-shaping roller supported by said movable head upstream of saidshaping rollers, said pre-shaping roller being adapted to initiatebending of I said strip around said mandrel, and actuating means for Iexerting pressure on said roller for rolling said'strip along saidgeneratrix.

l2..A machine according to claim 8, comprising a pair of shearingrollersmounted on said movable head downstream of said shaping rollers,and actuating -means for applyingpressure on said shearing rollers todetach from said strip portions along the lateral edges thereof.

13. A machine according to claim 12,, which, com prises a pair offolding rollers located upstreamofisaid shearing rollers for foldingsaid portions outwardly, said shearingvrollers being guided along thecreases formed in the strip by said folding rollers;

14. A method according to claim 2 which includes the step of welding theshaped part together where the,

edges of said strip have been cut off.

.15. Amachine according to claim 12, comprising a welding apparatussupported by said movable head I downstream of, said rollers forconnecting opposite adjacent edges on said shaped part where saidportions have been cut off.

1. A method of manufacturing from a strip of flat sheet metal a shapedelongated part having a progressively varying cross section, comprising:displacing said strip along a generatrix of a fixed shaping mandrel thecross section of which decreases progressively along said generatrix ina predetermined manner, and progressiveLy bending said strip as it isdisplaced around said mandrel on either side of said generatrix so as tofollow the shape and dimensions of said mandrel, by pressure means thepoint of action of which is variable along said mandrel to produce adesired variation in the cross section of the part to be shaped.
 2. Amethod according to claim 1, which includes the step of cutting theedges of said strip after having been bent around said mandrel as theshaped part progresses along said mandrel by cutting means associatedwith said pressure means.
 3. A method according to claim 2, whichincludes the step of folding said edges outwardly by folding meansassociated with said pressure means.
 4. A method according to claim 3,wherein said cutting means are guided along said mandrel by the foldline of the lateral edges produced by folding means.
 5. A methodaccording to claim 1, which includes subjecting said strip prior to saidshaping step to a softening heat treatment.
 6. A method according toclaim 1, which includes the step of subjecting said shaped part to ahardening heat treatment.
 7. A method according to claim 1, whichincludes the step of reciprocating said pressure means along saidmandrel and cutting the thus obtained shaped part intermittentaly.
 8. Amachine for manufacturing from a strip of flat sheet metal a shapedelongated part, comprising: a frame, a shaping mandrel mounted on saidframe and having a cross section decreasing progressively in onedirection at least one shaping head movable parallel to a generatrix ofsaid mandrel, at least one pair of shaping rollers and associatedactuating means supported by said head for urging said strip againstsaid shaping mandrel on either side of said generatrix, first drivemeans for displacing said strip at a uniform speed along saidgeneratrix, and second drive means for displacing said shaping head withrespect to said mandrel for producing the desired variation in crosssection of said part.
 9. A machine according to claim 8, wherein saidfirst drive means drives at least one of said pair of shaping rollers onsaid movable head.
 10. A machine according to claim 8, which includes abox mounted to slide on said movable head in a direction transverse tothe direction of displacement of said head, said shaping rollers beinglocated on said box, and a stationary slide associated with said mandrelfor guiding said box in said transverse direction.
 11. A machineaccording to claim 8, comprising at least one resilient pre-shapingroller supported by said movable head upstream of said shaping rollers,said pre-shaping roller being adapted to initiate bending of said striparound said mandrel, and actuating means for exerting pressure on saidroller for rolling said strip along said generatrix.
 12. A machineaccording to claim 8, comprising a pair of shearing rollers mounted onsaid movable head downstream of said shaping rollers, and actuatingmeans for applying pressure on said shearing rollers to detach from saidstrip portions along the lateral edges thereof.
 13. A machine accordingto claim 12, which comprises a pair of folding rollers located upstreamof said shearing rollers for folding said portions outwardly, saidshearing rollers being guided along the creases formed in the strip bysaid folding rollers.
 14. A method according to claim 2 which includesthe step of welding the shaped part together where the edges of saidstrip have been cut off.
 15. A machine according to claim 12, comprisinga welding apparatus supported by said movable head downstream of saidrollers for connecting opposite adjacent edges on said shaped part wheresaid portions have been cut off.